Saoirse Ronan, most recently seen kicking ass to techno music in Hanna, is set to be invaded. Ronan has been cast as Melanie, a young woman whose mind is besieged by a parasitic alien, in the film adaptation of The Host – a.k.a. that one Stephenie Meyer book that doesn’t involve pouty vampires.

The bestselling sci-fi novel follows Melanie and Wanderer, the extraterrestrial “soul” that has taken over her brain, as they experience a sort of paranormal Stockholm Syndrome. Ronan would play both roles, or more specifically, a role within a role, a daunting task that I’m sure the Oscar-nominated actress is more than up to. The film’s producers may be looking to make the character a bit younger: In the book, Melanie is 20 years old, while Ronan is 17.